The United Nations human rights investigator for Iran called on Friday for the immediate release of three Iranians with dual nationality whose health is a matter of concern. Ahmed Shaheed, UN special rapporteur on the situation of human rights in Iran, in particular highlighted the case of the Iranian-British aid worker Nazanin Zaghari-Ratcliffe, who was arrested in April with her 2-year-old daughter and tried in August. An Iranian revolutionary court sentenced her to five years in prison on charges that remain secret, her family said last month.

“Sentencing individuals for charges that are kept secret from defendants and their defence lawyers is a mockery of justice,” Shaheed, a former foreign minister of the Maldives, said in a statement. He said her health had “seriously deteriorated” since her arrest.

Zaghari-Ratcliffe works for the Thomson Reuters Foundation, a London-based charity that is independent of Reuters News. Her daughter, now also trapped in Iran, is being looked after by Zaghari-Ratcliffe’s parents.

Iran’s hardline Revolutionary Guards have accused Zaghari-Ratcliffe of trying to overthrow Iran’s clerical establishment, an accusation that the Foundation and her husband have dismissed.

“I am convinced of Nazanin’s innocence,” Thomson Reuters Foundation Chief Executive Monique Villa said in a statement. “She had no dealings with Iran whatsoever in her professional capacity as the Thomson Reuters Foundation does not operate in Iran, directly or indirectly.”

Iran does not recognise dual nationality, which prevents Western embassies from visiting such detainees. Shaheed said that two elderly men held in Tehran’s Evin prison required urgent medical attention and must also be freed.

Baquer Namazi, an 80-year-old retired official at the United Nations Children’s Fund (UNICEF) who also holds American nationality, has been detained since February on unknown charges and without access to a lawyer, Shaheed said.

A website ( http://freesiamak.com ) dedicated to freeing Namazi and his son Siamak, a businessman also being held in Iran, describes Baquer as an international civil servant and civil society volunteer. His supporters say on the site he has never been involved in any other business, activity or capacity.

Kamal Foroughi, 77, is an Iranian-British businessman arrested in May 2011 who is serving an eight-year prison term on charges of espionage and possession of alcoholic beverages, Shaheed said. Foroughi’s son, Kamran, told Britain’s Guardian newspaper last October. “My dad has always strenuously maintained his innocence and we believe him.”

Shaheed welcomed the release last month of Homa Hoodfar, an Iranian-Canadian national arrested in June. The Montreal academic was released a week after the two countries began talks on a